The harmonium and the accordion are two similar instruments working via the same core principles: free-reeds and bellows. Despite this commonality, the harmonium was popular in the late romanticism & early 20th century whilst the accordion, as a concert instrument, started to emerge only from the 1950s on; both instruments thus having a totally different repertoire. Nowadays however, it is not so easy to find a decent harmonium, let alone to come across somebody who masters its specific technique and for that reason, harmonium pieces are these days often performed on an accordion. This research will therefore try to be a guide for the accordion player who is asked to play a piece that was originally written for the harmonium, by providing him with some necessary tools and background information concerning the specifics of the harmonium. First of all, a brief history, focussing on the historical and constructional similarities and differences between both instruments, is included and besides that, the most common harmonium-types (compression system, suction system, art harmonium) aswel as the rise of the free-bass accordions are being described. The second chapter deals with the specific repertoire for the harmonium by offering a list containing the majority of the romantic literature for the instrument, written by established composers of that era. Hereby, some of the key compositions, e.g. l’Organiste by César Franck, are highlighted. A comparison between the way of playing, sound and registration of both instruments will conclude this thesis.
